I thought you might be interested in this site http://www.tobias-erichsen.de/software/loopmidi.html
It is a dynamic Midi patch cable like MidiYoke but it isn't an installable driver.
You create Midi ports as you need them.
Like MidiYoke it is great for examining what another program is putting out without using a loopback Midi cable in a hardware Midi interface.
Tobias offers the source code in a SDK.
I thought I would incorperate it in to a new project of mine, but I thought it would also be a good addition to MidiTools.
I want to extend a Roland Editor by putting my program between the editor and the synth using MidiYoke.
Strangely with every Midi patch cable I tried (Midi Yoke and LoopBE1) the Roland software stopped working but worked perfectly with Tobias' program.